Shock isolating device

ABSTRACT

A plastic shock isolator element composed of a hollow toroidallike body wherein its inside circumferential surface merges into a solid integral web centered upon and extending transversely to the axis of the toroidal-like body and its outside circumferential surface has an aperture which communicates with the interior thereof.

United States Patent Hardigg SHOCK ISOLATING DEVICE [72] Inventor: JamesS. Hardigg, P.O. Box 89,

Conway, Mass. 0 l 341 [22] Filed: Feb. 5, 1970 [21] Appl. No.: 9,017

[52] US. Cl. ..229/l4, 206/46, 267/141 [51] Int. Cl. ..B65d 25/12 [58]Field of Search ..267/l4l, 153, I40, 145, 63;

[56] References Cited UNITED STATES PATENTS Aninger ..206/46 FR [451Sept. 12,1972

3,192,978 7/1965 Horvath ..206l46 FR 3,242,964 3/1966 Mosshart etal...206/46 FR Primary Examiner-James B. Marbert Attorney'--Cushman, Darby8L Cushman [5 7] ABSTRACT A plastic shock isolator element composed of ahollow toroidal-like body wherein its inside circumferential surfacemerges into a solid integral web centered upon and extendingtransversely to the axis of the toroidallike body and its outsidecircumferential surface has an aperture which communicates with theinterior thereof.

. 19 Claims, 8 Drawing Figures SHOCK ISOLATING DEVICE This inventionrelates to a shock isolator element and to cushioned container unitshaving one or more shock isolator elements incorporated therein.

' Fragile articles, for example delicate machinery, instruments,electronic components and the like which are subject to damage by shock,severe vibration or similar forces, are customarily and necessarilypackaged in cushioned protective containers.

Typical cushioning devices are disclosed, for instance, in my US. Pats.No. 2,859,959; 3,003,622; 3,003,656; 3,283,988 and 3,445,553. Whilethese cushioning devices exhibit favorable dynamic and staticperformance characteristics, it was-found that these characteristicscould be retained or improved while at the same time the economicaspects of their manufacture could also be enhanced. As a result, the

A present invention, which departs considerably from the structuralconcept of the shock isolator elements shown in these patents, wasdeveloped. The shock isolator element of the present invention thusexhibits not only as favorable or better dynamic and staticcharacteristics of my earlier shock isolator elements, but the economicsof producing the present shock isolator elements have been significantlyimproved.

It is therefore a principal object of the present invention to provide anovel shock isolator element which can be utilized to build up cushionedcontainer units with conventional and readily available cartons, such ascorrugated fiberboard, wood, metal or plastic containers.

Yet another object of the'invention is to provide a shock isolatorelement exhibiting a unique combination of high shock absorption andstatic load capacities, adapted to efficiently and effectively protectfragile articles during storage, transportation and drops, which may beeither accidental or intentional, as in the case of air drops Theinvention and the novel features thereof can best be made clear byreference to the following description and the accompanying drawings, inwhich:

FIG. 1 is a perspective view of an exemplary embodiment of the shockisolator element, ready for incorporation into a container unit to becushioned;

FIG. 2 is a sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is a plan view of another embodiment of the shock isolatorelement of the present invention;

FIG. 4 is a sectional view taken on the line 4-4 of FIG. 3;

FIG. 5 is a plan view of another embodiment of the shock isolatorelement of the present invention;

FIG. 6 is a sectional view taken on the line 6-6 of FIG. 5;

FIG. 7 is a perspective view of another embodiment of the presentinvention; and

FIG. 8 is a sectional view taken on the line 8-8 of FIG. 7.

In the shipping and storage of articles, the articles are frequentlysubjected to G factors often in excess of 100 or greater, the G factorbeing an indication of the maximum acceleration a fragile body canwithstand without damage. For example, if the G factor of a givenarticle is 50, the article can safely be subjected to an acceleration 50times that of gravity. Further, during impact the acceleration to whichan article is subjected generally varies and the peak acceleration ratioduring the impact is termed Gm. The Gm value is valuable in determiningthe cushioning factor which is defined as where H is the drop height andT is the cushion thickness. The relationship of the cushioning factor tothe energy per unit volume impressed on the cushion, which can beexpressed as WXH T where W is weight of articles in pounds, and A is thearea under compression, can be determined through the use ofaccelerometers directly from impact tests of cushioning materialswithout establishing the stress strain curve.

Materials having a low minimum value are advantageously employed ascushioning materials. While the cushioning materials of the prior artsuch as foamed bodies provided with elastomeric columns providedfavorable dynamic and static performance characteristics, the presentinvention provides equally favorable or better performancecharacteristics and is more economical to produce.

GENERAL DESCRIPTION The shock isolator element of the present invention,broadly defined, is one which is characterized in that it possesses anappreciable degree of resistance to compressional forces and ondeformation restores itself to essentially its original shape. Theisolator element has spaced end walls and an intervening smooth sidewall. The end walls are relatively movable toward and away from eachother between a position of wide separation wherein the sidewall has adimension corresponding to its dimension in the undeformed state and aposition of close proximity wherein the sidewall-is collapsed.Additionally, the sidewall forms a continuous circular surface which,preferably, is outwardly convex. Also preferably an aperture is providedin the side wall of the shock isolator element which aperturecommunicates with the interior thereof.

The shock isolator element of the present invention comprises a hollowtoroidal-like body, the inside circumferential surface of which mergesinto a solid integral web centered upon and extending transversely tothe axis of the toroidal-like body. The outside circumferential surfaceof the toroidal-like body has an aperture communicating with theinterior of the shock isolator element.

Preferably, the outside circumferential surface of the shock isolatorelement of this invention is curved thereby providing more favorablerecovery characteristics after impact than a substantially straightwalled cylindrical configuration.

The ratio of thickness of the shock isolator element to its maximumdiameter can vary from about 0.33 to 0.66 although it will beappreciated that a ratio smaller or greater can also be employed.

. 3 Further, the ratio'of the diameter of the solid integral web formedfrom the inside circumferential surface of the hollow toroidal-like bodyto the thickness of the shock isolator element can vary between about0.25 to about 0.85, while the ratio of 'the diameter of the solidintegral web to the maximum diameter of the shock isolator element canpreferably vary between about 0.16 to about 0.28, the maximum diameterof the shock isolator element being dependent upon the use to which theshock isolator element is put. Conveniently,

shock isolator elements having a maximum diameter ranging from about 2 4inches to about 1 foot are preferred but elements with a larger maximumdiametercan be provided, for instance, when the element is employed as alanding attachment for helicopters.

The shock isolator element of this invention can be made of any suitablesynthetic thermoplastic material and preferably from polyvinyl chloride,polyurethane, polyethylene or polyethylene-EVA copolymers whichcopolymers, for instance, can have a ratio of the respective monomerranging generally from about 90:10 to :90.. Generally, any conventionalthermoforming process can be employed to produce the shock isolatorelements of this invention, although it has been found particularlyadvantageous to employ a blow molding technique in view of its readysusceptibility to mass production operations. The wall thickness of theshock isolator element of this invention is substantially uniformthroughout except at the integral web portion thereof which can be up toabout twice the wall thickness of the remainder. It has been foundpractical to provide a wall thickness (t) which is relatedto the maximumdiameter (D) of the shock isolator element by the followingrelationship. (t/D) is equal approximately to a value ranging betweenabout 0.007-0.03 and, preferably, between about 0.01-0.02. in manyinstances a convenient value for the ratio of (t/D) has been found to beabout 0.012. It will be recognized, however, that this value can varyslightly depending, for instance, on the particular material employed toproduce the shock isolator element as well as the ultimate use to whichthe element is put.

The following table illustrates the variance of the aperture sizerelative to such variables. Conveniently, when the shock isolatorelement has a maximum diameter ranging from about 2-12 inches, and athickness ranging from about 1-3 inches, the aperture can have adiameter up to about 0.312 inch.

TABLE Peak acceleration (gm.)

tached to a compatible backing member byconventional spin weldingtechniques although other heat welding processes can also be employed.When a spin welding technique is employed in assembling the shockisolator element to a backing member, at least the outer surface of theshock isolator element to be attached to the backing member ispreferably provided with at least one circular groove centered on theaxis of the toroidal-like body, the said surface being substantiallytangent to a plane normal to the axis of said body although it will berecognized that a groovelesssurface can also usefully be employed. Ithas further been found that even more desirable results can be achievedwhen a plurality of concentrically disposed grooves are provided.

Alternatively, a secondary backing member can be provided with anaperture into which the shock isolator assembly comprising the shockisolator element of this invention in association with a primary backingmember can be inserted and retained therein by interlocking engagementwith the secondary backing member. Conveniently a sun-burst'type openingin the secondary backing member can be utilized which providessufficient engagement with the shock isolator assembly to retain thelatter even under relatively severe transportation conditions;

SPECIFIC DESCRIPTION The shock isolator element of this invention may bemade more clear by referring to the drawings wherein, in FIG. 1 there isshown a three-faced, corner-shaped backing sheet 10, composed, forinstance, of polyethylene having attached to each of the three facesthereof a shock isolator element 12.

Each of said shock isolator elements 12 comprises a plastic, hollow,toroidal-like body, the inside circumferential surface 14 of whichmerges into the solid integral web 16 centered upon and extendingtransversely to the axis 18 (in dotted line) of the toroidal-like body.The outside circumferential surface 20 of the toroidal-like body isprovided with an aperture 22..

Preferably, the outside circumferential surface 20 is curved, and not ofa straight wall configuration.

As can be seen in FIG. 2, the solid integral web 16 lies on a mid-planepassing through the toroidal-like body 12 and is substantially normal tothe axis 18 Drop height (inches) 18 Load (lbs.) 1 set 24 Lofad (lbs.) 1set of o e 30 Load (lbs.) 1 set 36 Load (lbs.) 1 set 4 pads 4 pads 4pads of 4 pads Orifice size (inches) 30 40 60 70 30 40 50 60 70 30 40 5060 70 30 40 50 60 70 Sealed 45 36 32 29 27 48 40 36 35 33 49 47 45 45 4458 51 49 51 '55 4 35 31 29 27 46 39 35 33 32 47 44 42 39 39 e 49 45 4653 34 29 26 24 43 38 34 32 31 43 41 38 36 37 52 46 42 42 45 33 29 26 2343 37 33 30 29 44 39 36 34 34 53 43 40 41 46 32 28 24 22 45 35 30 26 2448 42 35 32 33 50 43 38 42 50 32 27 24 22 39 36 31 27 27 42 39 38 45 3145 40 46 52 Norm- Pad size 3" diarn ete r x 2 thick; pad weight gggranrspad made of low density polyethylene. A

The shock isolator element of this invention can be affixed or attachedto any suitable backing member by any convenient means such as by anadhesive or by mechanical fastening means such as rivets, screws, nailsor staples. Preferably, however, the shock isolator is atthereof.Alternatively, the solid integral web 16 can be substantially coplanarwith an outside surface 24 of the toroidal-like body, which outsidesurface 24 lies in a plane which is substantially normal to the axis 18of the toroidal-like body, as seen in FIG. 4.

The shock isolator element shown in FIGS. 1 and 2 was constructed ofpolyethylene in a blow-molding operation and had the followingdimensions: 1.5 inches thick, 3 inches in maximum diameter with anintegral web located at the midplane thereof. The integral web had adiameter measuring substantially one-half inch. The shock isolatorelement 12 was attached to the backing member, also madeof polyethylene,by a conventional heat welding operation.

To facilitate the assembly of the shock isolator element 12 to thebacking member by any convenient heat welding operation, such as aspin-welding technique, the outer surface 24 is provided with aplurality of circular grooves 26 which are centered on the axis 18 ofthe toroidallike body member. While a plurality of grooves 26 are shown,it will be apparent that as few as one groove 26 can be provided or morethan five as shown in this Figure. Also it is possible to provide one ormore grooves 26 on the corresponding but opposed surface 24', ifdesired. The grooves 26 have been found to improve the bond between theshock isolator element 12 and the backing member 10, especially when thebond is effected by a spin-welding technique.

The shock isolator element 12 shown in FIGS. 3 and 4 wasalso constructedof polyethylene in essentially the same manner as that used to producethe shock isolator element shown in FIGS. 1 and 2. In this embodiment,however, the shock isolator element has a maximum diameter of 3 inches,a thickness of 1.5 inches, the diameter of the integral web 16 beingsubstantially one-half inch. The integral web 16 is substantiallycoplanar with-the outside surface 24 which, in turn, lies in a planewhich is substantially normal to the axis 18. This embodiment lendsitself to attachment to a suitable backing member by mechanical meanssuch as nails, screws, rivets, staples and the like although certainlyconventional heat welding techniques can also be usefully employed toeffect such attachment.

The shock isolator element 12 shown in FIGS. 5 and 6 was alsoconstructed of polyethylene in much the same manner as the shockisolator element shown in FIGS. 1 and 2. However, the shock isolatorelement illustrated in FIGS. 5 and 6 is provided on the outsidecircumferential surface with a plurality of spaced projections 28. Aportion of said spaced projections lies in one plane passing throughsaid toroidal-like body slightly above the mid-plane thereof and normalto the axis thereof while another substantially equal portion of saidspaced projections lies on a second plane passing through saidtoroidal-like body slightly below the said mid-plane, which plane isalso normal to the axis thereof. In engagement with circumferential banddefined by the circumferential area between the projections lying on oneplane and the projections lying on said second plane is a backing memberprovided with an aperture having a size corresponding essentially to themaximum diameter of said toroidal-like body which is held in place byfurther engagement with said projections. Obviously, the thickness ofthe backing member chosen will determine the width of the band 30 andhence the placement of the projections 28 on said outsidecircumferential surface 20.

The shock isolator element 12 shown in FIGS. 7 and 8 is also constructedof polyethylene in essentially the same manner as the shock isolatorelements shown in FIGS. 1 and 2. A resilient backing member 10 which canbe hexagonal in shape is affixed thereto by a conventional spin-weldingtechnique. The resilient hexagonal shaped backing member will generallyhave a diameter larger than that of the toroidal-like body, and theassembly can be secured in place in a secondary or auxiliary backingmember 32 which can be made, for instance, of corrugated fiberboard orsheet by providing in the secondary backing member an aperture, themaximum size of which will be less than the diameter of the hexagonalshaped backing memberand less than the diameter of the toroidal-likebody member. The resilient backing member is fitted into the aperture sothat that portion of the secondary backing member, defined by theaperture, interlockingly engages both the backing member and thecircumferential surface of said toroidal-like member. As can be seen inFIG. 7, the aperture is in the form of a sun-burst die-cut and thesecondary backing member can be in the form of a generally L-shapedsection or any other convenient form or shape of corrugated fiberboardor any other convenient material which can be folded and secured intothe corner-shaped device shown in FIG. 1, with each face of the cornerbeing provided with a similar aperture in which an essentially similarisolator assembly is secured.

In another embodiment of the present invention, the ratio of thediameter of the integral web to the maximum diameter was increased andthe resulting shock isolator element more nearly resembled atoroidal-like body generated from a circle than the shock isolatorelements of FIGS. 1 and 2 which resemble a toroidallike body generatedfrom an ellipse. Nonetheless, this variation, due to an increase in theratio of the diameter of the integral web to the maximum diameter of thetoroidal-like body, exhibited quite favorable dynamic and staticcharacteristics as well as an acceptable recover of its initial shapefollowing impact.

The number of shock isolator elements of the present invention used toprovide a cushioned shipping container can vary widely and will dependon the nature and the size of the article being shipped as well as theanticipated forces to which the article will be subjected duringshipping or handling. Thus, in some instances, it may be necessary touse as many as 24 individual shock isolator elements where an articlepackaged in an inner rectangular container is provided with an outercontainer. Each face of the inner container will be provided with fourshock isolator elements to make a rotationally stable configuration,thereby accommodating all directions of impact. In other situations, notall faces of the container to be cushioned need be provided with fourshock isolator elements and as few as one shock isolator element on aface of the container can provide adequate protection.

It will also be appreciated that the shock isolator element of thepresent invention canbe employed in a manner other than in combinationwith an inner and outer container assembly. Thus, the shock isolatorelement can be positioned beneath large units that are shipped on skidsor pallets or they can be affixed to the ends of freight cars to reduceimpact forces when such cars are humped. They can also usefully beattached to, or form a part of, automobile bumpers as animprovecombination with conventional landing gear components forhelicopters, for instance, to-reduce the overall weight of thehelicopter which is especially desireable when the surface on which thehelicopter is i to land can safely support only a limited load. Stillother areas where the shock isolator element of the present inventioncan be used include the production of crash helmets where a plurality ofrelatively small shock isolator elements can form an inner liner for thehelmet. I

It is claimed:

, 1..A plastic shock isolator element comprising a ho]- lowtoroidal-like body having spaced end wallsand an intervening smooth sidewall with the inside circumferential surface of said body merging into asolid integral web centered upon and extending transversely to the axisof said toroidal-like body, said element possessing anappreciable degreeof resistance to compressional forces and on deformation restores itselfto essentially its original shape, said end walls being relativelymovable toward and away from each other between a position of wideseparation wherein the side wall has a dimension corresponding to itsdimension in the undeformed state and a position of close proximitywherein the side wall is collapsed.

2. The plastic shock isolator element of claim '1 wherein itsintervening smooth side wall has an aperture communicating with theinterior of said body.

3. The plastic shock isolator element of claim 1 wherein saidintervening smooth side wall is curved.

4. The plastic shock isolator element of claim 1 made of low densitypolyethylene.

' 5. The plastic shock isolator element of claim 1 wherein the solidintegral web lies on a mid-plane passing through said-toroidal-like bodynormal to the axis thereof.

6. The plastic shock isolator element of claim 1 is provided.

10. The plastic shock isolator of claim 9 wherein each of ,said endwalls isprovided with a plurality of said concentrically disposedgrooves.

l 1. The plastic shock isolator element of claim 1 including a backingsheet attached thereto substantially normal to the axis of saidtoroidal-like body.

2. A cushioned shipping container umtcomprismg anouter container adaptedto receive an article to be cushioned anda plurality of plastic shockisolator elements adapted to completely space said article from saidouter-container, each of said plastic shock isolator elements comprisinga hollow toroidal-like body having spaced end walls and an interveningsmooth side wall with the inside circumferential surface of said bodyforming a solid integral web centered upon and extending transversely tothe axis of saidtoroi'dal-like body, said element possessing anappreciable degree of resistance to compressional forces and ondeformation restores itself to essentially its original shape, said endwalls of each element being relatively movable toward and away from eachother between a position of wide separation wherein their associatedside wall has a dimension corresponding to its dimension in theundeformed state and a position of close proximity wherein said sidewall is collapsed.

13. The cushioned shipping container of claim 12 wherein the interveningside wall of each of said toroidal-like bodies is provided with anaperture.

14. The cushioned shipping container-unit of claim 12 wherein theplastic shock isolator element is made of low density polyethylene.

15. A hollow plastic shock isolator element which is characterized inthat it possesses an appreciable degree of resistance to compressionalforces and on deformation restores itself to essentially its originalshape com- 7 prising spaced end walls and an intervening smooth whereinthe solid integral web is substantially coplanar with an end wall ofsaid toroidal-like body, said end wall lying in a plane which issubstantially normal to the axis of said toroidal-like body.

7. The plastic shock isolator element of claim 2 wherein the aperture inthe intervening smooth side wall is located on a mid-plane passingthrough said to-- side wall having an aperture communicating with theinterior of said isolator element, said end walls being relativelymovable toward and away from each other between a position of wideseparation wherein the side wall has a dimension correspondingto itsdimension in the undeformed state and a position of close proximitywherein the side wall is collapsed.

16. The hollow plastic shock isolator element of claim 15 wherein theside wall forms a continuous circular surface.

17. The hollow plastic shock isolator element of claim 16 wherein thecontinuous circular surface is outwardly convex.

18. A plastic shock isolator element comprising a hollow toroidal-likebody, the outside circumferential surface of said toroidal-like bodyhaving an aperture communicating with the interior of said body.

19. The plastic shock isolator element of claim 18 wherein the outsidecircumferential surface is curved.

1. A plastic shock isolator element comprising a hollow toroidal-likebody having spaced end walls and an intervening smooth side wall withthe inside circumferEntial surface of said body merging into a solidintegral web centered upon and extending transversely to the axis ofsaid toroidal-like body, said element possessing an appreciable degreeof resistance to compressional forces and on deformation restores itselfto essentially its original shape, said end walls being relativelymovable toward and away from each other between a position of wideseparation wherein the side wall has a dimension corresponding to itsdimension in the undeformed state and a position of close proximitywherein the side wall is collapsed.
 2. The plastic shock isolatorelement of claim 1 wherein its intervening smooth side wall has anaperture communicating with the interior of said body.
 3. The plasticshock isolator element of claim 1 wherein said intervening smooth sidewall is curved.
 4. The plastic shock isolator element of claim 1 made oflow density polyethylene.
 5. The plastic shock isolator element of claim1 wherein the solid integral web lies on a mid-plane passing throughsaid toroidal-like body normal to the axis thereof.
 6. The plastic shockisolator element of claim 1 wherein the solid integral web issubstantially coplanar with an end wall of said toroidal-like body, saidend wall lying in a plane which is substantially normal to the axis ofsaid toroidal-like body.
 7. The plastic shock isolator element of claim2 wherein the aperture in the intervening smooth side wall is located ona mid-plane passing through said toroidal-like body normal to the axisthereof.
 8. The plastic shock isolator element of claim 1 wherein atleast one end wall of said toroidal-like body is provided with acircular groove centered on the axis of said toroidal-like body, saidend wall being substantially tangent to a plane normal to the axis ofsaid body.
 9. The plastic shock isolator element of claim 8 wherein aplurality of concentrically disposed grooves is provided.
 10. Theplastic shock isolator of claim 9 wherein each of said end walls isprovided with a plurality of said concentrically disposed grooves. 11.The plastic shock isolator element of claim 1 including a backing sheetattached thereto substantially normal to the axis of said toroidal-likebody.
 12. A cushioned shipping container unit comprising an outercontainer adapted to receive an article to be cushioned and a pluralityof plastic shock isolator elements adapted to completely space saidarticle from said outer container, each of said plastic shock isolatorelements comprising a hollow toroidal-like body having spaced end wallsand an intervening smooth side wall with the inside circumferentialsurface of said body forming a solid integral web centered upon andextending transversely to the axis of said toroidal-like body, saidelement possessing an appreciable degree of resistance to compressionalforces and on deformation restores itself to essentially its originalshape, said end walls of each element being relatively movable towardand away from each other between a position of wide separation whereintheir associated side wall has a dimension corresponding to itsdimension in the undeformed state and a position of close proximitywherein said side wall is collapsed.
 13. The cushioned shippingcontainer of claim 12 wherein the intervening side wall of each of saidtoroidal-like bodies is provided with an aperture.
 14. The cushionedshipping container unit of claim 12 wherein the plastic shock isolatorelement is made of low density polyethylene.
 15. A hollow plastic shockisolator element which is characterized in that it possesses anappreciable degree of resistance to compressional forces and ondeformation restores itself to essentially its original shape comprisingspaced end walls and an intervening smooth side wall, said end wallsbeing relatively movable toward and away from each other between aposition of wide separation wherein the side wall has a dimensioncorresponding to its dimension in the undeformed state and a position ofclose proxiMity wherein the side wall is collapsed.
 16. The hollowplastic shock isolator element of claim 15 wherein the side wall forms acontinuous circular surface.
 17. The hollow plastic shock isolatorelement of claim 16 wherein the continuous circular surface is outwardlyconvex.
 18. The hollow plastic shock isolator element of claim 15wherein an aperture is provided in the side wall.
 19. A plastic shockisolator element comprising a hollow toroidal-like body.
 20. The plasticshock isolator element of claim 19 wherein the outside circumferentialsurface of said toroidal-like body has an aperture communicating withthe interior of said body.
 21. The plastic shock isolator element ofclaim 20 wherein the outside circumferential surface is curved.